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Synaptic Transmission

Synaptic Transmission. Lesson 11. Synapses. Signaling between neurons chemical few electric Chemical synapse types axodendritic axosomatic axoaxonic dendrodendritic ~. Synaptic Events. Action Potential reaches axon terminal Chemical substance released Neurotransmitter (NT)

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Synaptic Transmission

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  1. Synaptic Transmission Lesson 11

  2. Synapses • Signaling between neurons • chemical • few electric • Chemical synapse types • axodendritic • axosomatic • axoaxonic • dendrodendritic ~

  3. Synaptic Events • Action Potential reaches axon terminal • Chemical substance released • Neurotransmitter (NT) • Diffuses across synapse • Binds to receptor protein • EPSP or IPSP ~

  4. Synaptic Transmission Model 1. Precursor transport 2. NT synthesis 3. Storage 4. Release 5. Activation 6. Termination ~

  5. Postsynaptic Membrane Presynaptic Axon Terminal Dendritic Spine Terminal Button

  6. 1. Precursor Transport

  7. 2. Synthesis • Enzymes & cofactors • Can be multiple steps ~ E

  8. 3. Storage In vesicles E

  9. 3. Storage In vesicles Terminal Button Dendritic Spine Synapse

  10. AP Ca++ 4. Release Synapse

  11. Ca++ 4. Release diffusion

  12. 5. Activation • NT binds to receptor

  13. Activation • NT binds to postsynaptic receptor • opens ion channel • EPSP • or IPSP ~

  14. 6. Termination • 4 Basic methods • Diffusion • Enzymatic degradation • Presynaptic reuptake • active transport • Autoreceptors ~

  15. 6. Termination E A RU E

  16. Autoreceptors • On presynaptic terminal • Binds NT • same as postsynaptic receptors • different receptor subtype • Decreases NT release & synthesis • via 2d messenger system ~

  17. Termination • Must have discrete signal • What if ion channels continually open? • Disrupts neural communication • Termination  neuron repolarizes ~

  18. Drug Interaction Terms • Drug’s effect on synaptic transmission • Direct  at postsynaptic receptor • Indirect  at any other step • Agonist (AG) • mimics or ­NT effects • Antagonist (ANT) • blocks or ¯NT effects ~

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